Starbucks Shortbread:
1 cup butter (2 sticks), room temperature
3/4 cup sugar
2 teaspoons vanilla
2 cups wheat flour
1/4 teaspoon salt
Use an electric mixer to cream butter, sugar, and vanilla.
In a medium-sized bowl, combine the flour and salt.
Gradually incorporate the flour mixture to the butter and sugar; mixing until smooth.
Divide the dough in half and shape it into two balls. Wrap each ball in plastic and chill in the refrigerator for 30 minutes.
Starbucks Brown Sugar Filling:
1/3 cup powdered sugar
1/4 cup brown sugar
1 tablespoon cinnamon
1 teaspoon vanilla
1/4 cup toasted walnuts, finely chopped
1 tablespoon liquid egg white
In a medium-sized bowl, combine the confectioners sugar, brown sugar, and cinnamon.
In a separate bowl, combine the liquid egg white and vanilla; Add the walnuts and toss to coat.
Combine the sugar mixture with the walnut mixture and stir until smooth.
To prepare:
Preheat the oven to 350 F.
Line a cookie sheet with parchment paper.
Roll out one ball of chilled dough onto a floured surface to 1/8 inch thick.
Cut the dough into 16 2 x 4 inch rectangles.
Place 8 rectangles onto a parchment lined cookie sheet and place 1 tablespoon of filling in the center of each rectangle.
Place a second shortbread rectangle on top of the filling and crimp the edges with the tines of a fork. Poke some holes in the top shortbread crust to allow steam to escape while cooking.[6]
Repeat this process with the second ball or dough.
Bake the tarts for 8 to 10 minutes, until the edges are lightly brown.
Allow the tarts to cool on the cookie sheet for a few minutes before moving them to a cooling rack.